Infrared signal based position recognition system for use with a robot-assisted surgery

ABSTRACT

An improved device for regenerating an infrared signal transmitted over the air for use in detecting a 3-dimensional position of an object. The regeneration device includes an infrared signal transmitter and detector that receives from the object a responsive infrared signal in response to the infrared signal transmitted by the transmitter. A low pass filter receives the responsive infrared signal from the detector and outputs a low-pass filtered signal. A comparator compares the output of the infrared signal detector and output of the low pass filter and generates an output representing a logic state based on the comparison.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/260,249, filed on Jan. 29, 2019 (published as U.S. Pat. Pub. No.2019-0239964), which is a divisional patent application of U.S. patentapplication Ser. No. 15/135,658, filed on Apr. 22, 2016 (now U.S. Pat.No. 10,231,791), which is a continuation-in-part of U.S. patentapplication Ser. No. 15/095,883, filed Apr. 11, 2016 (published as U.S.Pat. Pub. No. 2016-0220320), which is a continuation-in-part of U.S.patent application Ser. No. 14/062,707 (now U.S. Pat. No. 10,357,184),filed on Oct. 24, 2013, which is a continuation-in-part application ofU.S. patent application Ser. No. 13/924,505, filed on Jun. 21, 2013 (nowU.S. Pat. No. 9,782,229), which claims priority to provisionalapplication No. 61/662,702 filed on Jun. 21, 2012 (expired) and claimspriority to provisional application No. 61/800,527 filed on Mar. 15,2013 (expired), all of which are incorporated by reference herein intheir entireties for all purposes.

FIELD

The present disclosure relates to position recognition systems and inparticular, infrared based position recognition system for use with arobot assisted surgery.

BACKGROUND

Position recognition systems are used to determine the position of andtrack a particular object in 3-dimensions. In robot assisted surgeries,for example, certain objects, such as a surgical instrument, needs to betracked with a high degree of precision as the instrument is beingpositioned and moved by a physician.

An infrared signal based position recognition systems use either passivesensors or active sensors. In passive sensors, objects to be trackedsuch as spherical balls are positioned at strategic locations of theobject to be tracked. Infrared transmitters transmit a signal having apredetermined waveform pattern. The spherical balls reflect the signaland the reflected signals are received by infrared signal detectors thatare generally located near the transmitters.

In active sensors, the objects to be tracked have their own infraredtransmitters and thus generate their own infrared signals in response tothe signals transmitted from an infrared transmitter of the positionrecognition system.

In either active or passive sensors, the responsive infrared signalsfrom the objects to be tracked are received and amplified in a formwhich is as close to the original infrared signals as possible. Theamplified signal is then converted into a digital signal which is usableby a signal processor. The system then geometrically resolves the3-dimensional position of the spherical balls based on one or more ofthe converted digital signals, cameras, digital waveform shape of theamplified signals, known locations of the spherical balls, distance, thetime it took to receive the responsive signals, or a combinationthereof.

One problem is that due to attenuation of infrared signals, theconventional position recognition systems have a relatively limitedworking range of distance between the system and objects to be tracked.Typically, the working range is limited to about 3-5 meters, at best,before the amplified signal loses sufficient original waveforminformation to be useful.

Moreover, conventional systems require relatively high bandwidth, highslew rate amplifiers which involve complex and expensive circuits.Therefore there is a need to provide an improved system and method forrecognizing the 3-dimensional position of an object, which has a longerworking range, is accurate, and is less expensive.

SUMMARY

To meet this and other needs, devices, systems, and methods fordetermining the 3-dimensional position of an object is provided. Forexample, an improved device for regenerating an infrared signaltransmitted over the air for use in detecting a 3-dimensional positionof an object is provided.

According to one embodiment, a surgical robot system includes a robothaving a robot base and a display, a robot arm coupled to the robotbase, and an end-effector coupled to the robot arm, the end-effectorhaving one or more tracking markers, wherein movement of theend-effector is electronically controlled by the robot. The systemfurther includes a camera stand including at least one camera able todetect the one or more tracking markers, the camera including at leastone infrared signal detector that receives from the one or more trackingmarkers an infrared signal, wherein the robot determines a 3-dimensionalposition of the one or more tracking markers based on the infraredsignal, and wherein the infrared signal includes a burst signal. Theinfrared signal may include a burst pattern including the burst signalfor a fixed amount of time and a non-burst signal for a fixed amount oftime.

According to another embodiment, the regeneration device includes aninfrared signal transmitter and an infrared signal detector thatreceives from the object a responsive infrared signal in response to theinfrared signal transmitted by the infrared transmitter. A low passfilter receives the responsive infrared signal from the detector andoutputs a low-pass filtered signal. A comparator has a first inputconnected to the output of the infrared signal detector and a secondinput connected to the output of the low pass filter. The comparatorgenerates an output representing a logic state based on comparisonbetween the first and second inputs.

Advantageously, the present invention relaxes the requirement of a highbandwidth, high slew output amplification and allows positionrecognition of the object over a longer distance due to less sensitivityof the signal amplitude variation.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overhead view of a potential arrangement for locations ofthe robotic system, patient, surgeon, and other medical personnel duringa surgical procedure;

FIG. 2 illustrates the robotic system including positioning of thesurgical robot and the camera relative to the patient according to oneembodiment;

FIG. 3 illustrates a surgical robotic system in accordance with anexemplary embodiment;

FIG. 4 illustrates a portion of a surgical robot in accordance with anexemplary embodiment;

FIG. 5 illustrates a block diagram of a surgical robot in accordancewith an exemplary embodiment;

FIG. 6 illustrates a surgical robot in accordance with an exemplaryembodiment;

FIGS. 7A-7C illustrate an end-effector in accordance with an exemplaryembodiment;

FIG. 8 illustrates a surgical instrument and the end effector, beforeand after, inserting the surgical instrument into the guide tube of theend effector according to one embodiment;

FIGS. 9A-9C illustrate portions of an end-effector and robot arm inaccordance with an exemplary embodiment;

FIG. 10 illustrates a dynamic reference array, an imaging array, andother components in accordance with an exemplary embodiment;

FIG. 11 illustrates a method of registration in accordance with anexemplary embodiment;

FIG. 12A-12B illustrate embodiments of imaging devices according toexemplary embodiments;

FIG. 13 is a waveform of an exemplary infrared signal;

FIG. 14 is a functional diagram of an infrared signal regenerationcircuit according to one embodiment;

FIG. 15 is a functional diagram of an infrared signal based positionrecognition system for use with a robot-assisted surgery according toone aspect; and

FIG. 16 is a graph illustrating signal outputs at various nodes of theinfrared signal regeneration circuit of FIG. 14.

DETAILED DESCRIPTION

It is to be understood that the present disclosure is not limited in itsapplication to the details of construction and the arrangement ofcomponents set forth in the description herein or illustrated in thedrawings. The teachings of the present disclosure may be used andpracticed in other embodiments and practiced or carried out in variousways. Also, it is to be understood that the phraseology and terminologyused herein is for the purpose of description and should not be regardedas limiting. The use of “including,” “comprising,” or “having” andvariations thereof herein is meant to encompass the items listedthereafter and equivalents thereof as well as additional items. Unlessspecified or limited otherwise, the terms “mounted,” “connected,”“supported,” and “coupled” and variations thereof are used broadly andencompass both direct and indirect mountings, connections, supports, andcouplings. Further, “connected” and “coupled” are not restricted tophysical or mechanical connections or couplings.

The following discussion is presented to enable a person skilled in theart to make and use embodiments of the present disclosure. Variousmodifications to the illustrated embodiments will be readily apparent tothose skilled in the art, and the principles herein can be applied toother embodiments and applications without departing from embodiments ofthe present disclosure. Thus, the embodiments are not intended to belimited to embodiments shown, but are to be accorded the widest scopeconsistent with the principles and features disclosed herein. Thefollowing detailed description is to be read with reference to thefigures, in which like elements in different figures have like referencenumerals. The figures, which are not necessarily to scale, depictselected embodiments and are not intended to limit the scope of theembodiments. Skilled artisans will recognize the examples providedherein have many useful alternatives and fall within the scope of theembodiments.

FIGS. 1 and 2 illustrate a surgical robot system 100 in accordance withan exemplary embodiment. Surgical robot system 100 may include, forexample, a surgical robot 102, one or more robot arms 104, a base 106, adisplay 110, an end-effector 112, for example, including a guide tube114, and one or more tracking markers 118. The surgical robot system 100may include a patient tracking device 116 also including one or moretracking markers 118, which is adapted to be secured directly to thepatient 210 (e.g., to the bone of the patient 210). The surgical robotsystem 100 may also utilize a camera 200, for example, positioned on acamera stand 202. The camera stand 202 can have any suitableconfiguration to move, orient, and support the camera 200 in a desiredposition. The camera 200 may include any suitable camera or cameras,such as one or more infrared cameras (e.g., bifocal cameras), able toidentify, for example, active and passive tracking markers 118 in agiven measurement volume viewable from the perspective of the camera200. The camera 200 may scan the given measurement volume and detect thelight that comes from the markers 118 in order to identify and determinethe position of the markers 118 in three-dimensions. For example, activemarkers 118 may include infrared-emitting markers that are activated byan electrical signal (e.g., infrared light emitting diodes (LEDs)), andpassive markers 118 may include retro-reflective markers that reflectinfrared light (e.g., they reflect incoming IR radiation into thedirection of the incoming light), for example, emitted by illuminatorson the camera 200 or other suitable device.

FIGS. 1 and 2 illustrate a potential configuration for the placement ofthe surgical robot system 100 in an operating room environment. Forexample, the robot 102 may be positioned near or next to patient 210.Although depicted near the head of the patient 210, it will beappreciated that the robot 102 can be positioned at any suitablelocation near the patient 210 depending on the area of the patient 210undergoing the operation. The camera 200 may be separated from the robotsystem 100 and positioned at the foot of patient 210. This locationallows the camera 200 to have a direct visual line of sight to thesurgical field 208. Again, it is contemplated that the camera 200 may belocated at any suitable position having line of sight to the surgicalfield 208. In the configuration shown, the surgeon 120 may be positionedacross from the robot 102, but is still able to manipulate theend-effector 112 and the display 110. A surgical assistant 126 may bepositioned across from the surgeon 120 again with access to both theend-effector 112 and the display 110. If desired, the locations of thesurgeon 120 and the assistant 126 may be reversed. The traditional areasfor the anesthesiologist 122 and the nurse or scrub tech 124 remainunimpeded by the locations of the robot 102 and camera 200.

With respect to the other components of the robot 102, the display 110can be attached to the surgical robot 102 and in other exemplaryembodiments, display 110 can be detached from surgical robot 102, eitherwithin a surgical room with the surgical robot 102, or in a remotelocation. End-effector 112 may be coupled to the robot arm 104 andcontrolled by at least one motor. In exemplary embodiments, end-effector112 can comprise a guide tube 114, which is able to receive and orient asurgical instrument 608 (described further herein) used to performsurgery on the patient 210. As used herein, the term “end-effector” isused interchangeably with the terms “end-effectuator” and “effectuatorelement.” Although generally shown with a guide tube 114, it will beappreciated that the end-effector 112 may be replaced with any suitableinstrumentation suitable for use in surgery. In some embodiments,end-effector 112 can comprise any known structure for effecting themovement of the surgical instrument 608 in a desired manner.

The surgical robot 102 is able to control the translation andorientation of the end-effector 112. The robot 102 is able to moveend-effector 112 along x-, y-, and z-axes, for example. The end-effector112 can be configured for selective rotation about one or more of thex-, y-, and z-axis, and a Z Frame axis (such that one or more of theEuler Angles (e.g., roll, pitch, and/or yaw) associated withend-effector 112 can be selectively controlled). In some exemplaryembodiments, selective control of the translation and orientation ofend-effector 112 can permit performance of medical procedures withsignificantly improved accuracy compared to conventional robots thatutilize, for example, a six degree of freedom robot arm comprising onlyrotational axes. For example, the surgical robot system 100 may be usedto operate on patient 210, and robot arm 104 can be positioned above thebody of patient 210, with end-effector 112 selectively angled relativeto the z-axis toward the body of patient 210.

In some exemplary embodiments, the position of the surgical instrument608 can be dynamically updated so that surgical robot 102 can be awareof the location of the surgical instrument 608 at all times during theprocedure. Consequently, in some exemplary embodiments, surgical robot102 can move the surgical instrument 608 to the desired position quicklywithout any further assistance from a physician (unless the physician sodesires). In some further embodiments, surgical robot 102 can beconfigured to correct the path of the surgical instrument 608 if thesurgical instrument 608 strays from the selected, preplanned trajectory.In some exemplary embodiments, surgical robot 102 can be configured topermit stoppage, modification, and/or manual control of the movement ofend-effector 112 and/or the surgical instrument 608. Thus, in use, inexemplary embodiments, a physician or other user can operate the system100, and has the option to stop, modify, or manually control theautonomous movement of end-effector 112 and/or the surgical instrument608. Further details of surgical robot system 100 including the controland movement of a surgical instrument 608 by surgical robot 102 can befound in co-pending U.S. patent application Ser. No. 13/924,505, whichis incorporated herein by reference in its entirety.

The robotic surgical system 100 can comprise one or more trackingmarkers 118 configured to track the movement of robot arm 104,end-effector 112, patient 210, and/or the surgical instrument 608 inthree dimensions. In exemplary embodiments, a plurality of trackingmarkers 118 can be mounted (or otherwise secured) thereon to an outersurface of the robot 102, such as, for example and without limitation,on base 106 of robot 102, on robot arm 104, or on the end effector 112.In exemplary embodiments, at least one tracking marker 118 of theplurality of tracking markers 118 can be mounted or otherwise secured tothe end-effector 112. One or more tracking markers 118 can further bemounted (or otherwise secured) to the patient 210. In exemplaryembodiments, the plurality of tracking markers 118 can be positioned onthe patient 210 spaced apart from the surgical field 208 to reduce thelikelihood of being obscured by the surgeon, surgical tools, or otherparts of the robot 102. Further, one or more tracking markers 118 can befurther mounted (or otherwise secured) to the surgical tools 608 (e.g.,a screw driver, dilator, implant inserter, or the like). Thus, thetracking markers 118 enable each of the marked objects (e.g., the endeffector 112, the patient 210, and the surgical tools 608) to be trackedby the robot 102. In exemplary embodiments, system 100 can use trackinginformation collected from each of the marked objects to calculate theorientation and location, for example, of the end effector 112, thesurgical instrument 608 (e.g., positioned in the tube 114 of the endeffector 112), and the relative position of the patient 210.

In exemplary embodiments, one or more of markers 118 may be opticalmarkers. In some embodiments, the positioning of one or more trackingmarkers 118 on end-effector 112 can maximize the accuracy of thepositional measurements by serving to check or verify the position ofend-effector 112. Further details of surgical robot system 100 includingthe control, movement and tracking of surgical robot 102 and of asurgical instrument 608 can be found in co-pending U.S. patentapplication Ser. No. 13/924,505, which is incorporated herein byreference in its entirety.

Exemplary embodiments include one or more markers 118 coupled to thesurgical instrument 608. In exemplary embodiments, these markers 118,for example, coupled to the patient 210 and surgical instruments 608, aswell as markers 118 coupled to the end effector 112 of the robot 102 cancomprise conventional infrared light-emitting diodes (LEDs) or anOptotrak® diode capable of being tracked using a commercially availableinfrared optical tracking system such as Optotrak®. Optotrak® is aregistered trademark of Northern Digital Inc., Waterloo, Ontario,Canada. In other embodiments, markers 118 can comprise conventionalreflective spheres capable of being tracked using a commerciallyavailable optical tracking system such as Polaris Spectra. PolarisSpectra is also a registered trademark of Northern Digital, Inc. In anexemplary embodiment, the markers 118 coupled to the end effector 112are active markers which comprise infrared light-emitting diodes whichmay be turned on and off, and the markers 118 coupled to the patient 210and the surgical instruments 608 comprise passive reflective spheres.

In exemplary embodiments, light emitted from and/or reflected by markers118 can be detected by camera 200 and can be used to monitor thelocation and movement of the marked objects. In alternative embodiments,markers 118 can comprise a radio-frequency and/or electromagneticreflector or transceiver and the camera 200 can include or be replacedby a radio-frequency and/or electromagnetic transceiver.

Similar to surgical robot system 100, FIG. 3 illustrates a surgicalrobot system 300 and camera stand 302, in a docked configuration,consistent with an exemplary embodiment of the present disclosure.Surgical robot system 300 may comprise a robot 301 including a display304, upper arm 306, lower arm 308, end-effector 310, vertical column312, casters 314, cabinet 316, tablet drawer 318, connector panel 320,control panel 322, and ring of information 324. Camera stand 302 maycomprise camera 326. These components are described in greater withrespect to FIG. 5. FIG. 3 illustrates the surgical robot system 300 in adocked configuration where the camera stand 302 is nested with the robot301, for example, when not in use. It will be appreciated by thoseskilled in the art that the camera 326 and robot 301 may be separatedfrom one another and positioned at any appropriate location during thesurgical procedure, for example, as shown in FIGS. 1 and 2.

FIG. 4 illustrates a base 400 consistent with an exemplary embodiment ofthe present disclosure. Base 400 may be a portion of surgical robotsystem 300 and comprise cabinet 316. Cabinet 316 may house certaincomponents of surgical robot system 300 including but not limited to abattery 402, a power distribution module 404, a platform interface boardmodule 406, a computer 408, a handle 412, and a tablet drawer 414. Theconnections and relationship between these components is described ingreater detail with respect to FIG. 5.

FIG. 5 illustrates a block diagram of certain components of an exemplaryembodiment of surgical robot system 300. Surgical robot system 300 maycomprise platform subsystem 502, computer subsystem 504, motion controlsubsystem 506, and tracking subsystem 532. Platform subsystem 502 mayfurther comprise battery 402, power distribution module 404, platforminterface board module 406, and tablet charging station 534. Computersubsystem 504 may further comprise computer 408, display 304, andspeaker 536. Motion control subsystem 506 may further comprise drivercircuit 508, motors 510, 512, 514, 516, 518, stabilizers 520, 522, 524,526, end-effector 310, and controller 538. Tracking subsystem 532 mayfurther comprise position sensor 540 and camera converter 542. System300 may also comprise a foot pedal 544 and tablet 546.

Input power is supplied to system 300 via a power source 548 which maybe provided to power distribution module 404. Power distribution module404 receives input power and is configured to generate different powersupply voltages that are provided to other modules, components, andsubsystems of system 300. Power distribution module 404 may beconfigured to provide different voltage supplies to platform interfacemodule 406, which may be provided to other components such as computer408, display 304, speaker 536, driver 508 to, for example, power motors512, 514, 516, 518 and end-effector 310, motor 510, ring 324, cameraconverter 542, and other components for system 300 for example, fans forcooling the electrical components within cabinet 316.

Power distribution module 404 may also provide power to other componentssuch as tablet charging station 534 that may be located within tabletdrawer 318. Tablet charging station 534 may be in wireless or wiredcommunication with tablet 546 for charging table 546. Tablet 546 may beused by a surgeon consistent with the present disclosure and describedherein.

Power distribution module 404 may also be connected to battery 402,which serves as temporary power source in the event that powerdistribution module 404 does not receive power from input power 548. Atother times, power distribution module 404 may serve to charge battery402 if necessary.

Other components of platform subsystem 502 may also include connectorpanel 320, control panel 322, and ring 324. Connector panel 320 mayserve to connect different devices and components to system 300 and/orassociated components and modules. Connector panel 320 may contain oneor more ports that receive lines or connections from differentcomponents. For example, connector panel 320 may have a ground terminalport that may ground system 300 to other equipment, a port to connectfoot pedal 544 to system 300, a port to connect to tracking subsystem532, which may comprise position sensor 540, camera converter 542, andcameras 326 associated with camera stand 302. Connector panel 320 mayalso include other ports to allow USB, Ethernet, HDMI communications toother components, such as computer 408.

Control panel 322 may provide various buttons or indicators that controloperation of system 300 and/or provide information regarding system 300.For example, control panel 322 may include buttons to power on or offsystem 300, lift or lower vertical column 312, and lift or lowerstabilizers 520-526 that may be designed to engage casters 314 to locksystem 300 from physically moving. Other buttons may stop system 300 inthe event of an emergency, which may remove all motor power and applymechanical brakes to stop all motion from occurring. Control panel 322may also have indicators notifying the user of certain system conditionssuch as a line power indicator or status of charge for battery 402.

Ring 324 may be a visual indicator to notify the user of system 300 ofdifferent modes that system 300 is operating under and certain warningsto the user.

Computer subsystem 504 includes computer 408, display 304, and speaker536. Computer 504 includes an operating system and software to operatesystem 300. Computer 504 may receive and process information from othercomponents (for example, tracking subsystem 532, platform subsystem 502,and/or motion control subsystem 506) in order to display information tothe user. Further, computer subsystem 504 may also include speaker 536to provide audio to the user.

Tracking subsystem 532 may include position sensor 504 and converter542. Tracking subsystem 532 may correspond to camera stand 302 includingcamera 326 as described with respect to FIG. 3. Position sensor 504 maybe camera 326. Tracking subsystem may track the location of certainmarkers that are located on the different components of system 300and/or instruments used by a user during a surgical procedure. Thistracking may be conducted in a manner consistent with the presentdisclosure including the use of infrared technology that tracks thelocation of active or passive elements, such as LEDs or reflectivemarkers, respectively. The location, orientation, and position ofstructures having these types of markers may be provided to computer 408which may be shown to a user on display 304. For example, a surgicalinstrument 608 having these types of markers and tracked in this manner(which may be referred to as a navigational space) may be shown to auser in relation to a three dimensional image of a patient's anatomicalstructure.

Motion control subsystem 506 may be configured to physically movevertical column 312, upper arm 306, lower arm 308, or rotateend-effector 310. The physical movement may be conducted through the useof one or more motors 510-518. For example, motor 510 may be configuredto vertically lift or lower vertical column 312. Motor 512 may beconfigured to laterally move upper arm 308 around a point of engagementwith vertical column 312 as shown in FIG. 3. Motor 514 may be configuredto laterally move lower arm 308 around a point of engagement with upperarm 308 as shown in FIG. 3. Motors 516 and 518 may be configured to moveend-effector 310 in a manner such that one may control the roll and onemay control the tilt, thereby providing multiple angles thatend-effector 310 may be moved. These movements may be achieved bycontroller 538 which may control these movements through load cellsdisposed on end-effector 310 and activated by a user engaging these loadcells to move system 300 in a desired manner.

Moreover, system 300 may provide for automatic movement of verticalcolumn 312, upper arm 306, and lower arm 308 through a user indicatingon display 304 (which may be a touchscreen input device) the location ofa surgical instrument or component on three dimensional image of thepatient's anatomy on display 304. The user may initiate this automaticmovement by stepping on foot pedal 544 or some other input means.

FIG. 6 illustrates a surgical robot system 600 consistent with anexemplary embodiment. Surgical robot system 600 may compriseend-effector 602, robot arm 604, guide tube 606, instrument 608, androbot base 610. Instrument tool 608 may be attached to a tracking array612 including one or more tracking markers (such as markers 118) andhave an associated trajectory 614. Trajectory 614 may represent a pathof movement that instrument tool 608 is configured to travel once it ispositioned through or secured in guide tube 606, for example, a path ofinsertion of instrument tool 608 into a patient. In an exemplaryoperation, robot base 610 may be configured to be in electroniccommunication with robot arm 604 and end-effector 602 so that surgicalrobot system 600 may assist a user (for example, a surgeon) in operatingon the patient 210. Surgical robot system 600 may be consistent withpreviously described surgical robot system 100 and 300.

A tracking array 612 may be mounted on instrument 608 to monitor thelocation and orientation of instrument tool 608. The tracking array 612may be attached to an instrument 608 and may comprise tracking markers804. As best seen in FIG. 8, tracking markers 804 may be, for example,light emitting diodes and/or other types of reflective markers (e.g.,markers 118 as described elsewhere herein). The tracking devices may beone or more line of sight devices associated with the surgical robotsystem. As an example, the tracking devices may be one or more cameras200, 326 associated with the surgical robot system 100, 300 and may alsotrack tracking array 612 for a defined domain or relative orientationsof the instrument 608 in relation to the robot arm 604, the robot base610, end-effector 602, and/or the patient 210. The tracking devices maybe consistent with those structures described in connection with camerastand 302 and tracking subsystem 532.

FIGS. 7A, 7B, and 7C illustrate a top view, front view, and side view,respectively, of end-effector 602 consistent with an exemplaryembodiment. End-effector 602 may comprise one or more tracking markers702. Tracking markers 702 may be light emitting diodes or other types ofactive and passive markers, such as tracking markers 118 that have beenpreviously described. In an exemplary embodiment, the tracking markers702 are active infrared-emitting markers that are activated by anelectrical signal (e.g., infrared light emitting diodes (LEDs)). Thus,tracking markers 702 may be activated such that the infrared markers 702are visible to the camera 200, 326 or may be deactivated such that theinfrared markers 702 are not visible to the camera 200, 326. Thus, whenthe markers 702 are active, the end effector 602 may be controlled bythe system 100, 300, 600, and when the markers 702 are deactivated, theend effector 602 may be locked in position and unable to be moved by thesystem 100, 300, 600.

Markers 702 may be disposed on or within end-effector 602 in a mannersuch that the markers 702 are visible by one or more cameras 200, 326 orother tracking devices associated with the surgical robot system 100,300, 600. The camera 200, 326 or other tracking devices may trackend-effector 602 as it moves to different positions and viewing anglesby following the movement of tracking markers 702. The location ofmarkers 702 and/or end-effector 602 may be shown on a display 110, 304associated with the surgical robot system 100, 300, 600, for example,display 110 as shown in FIG. 2 and/or display 304 shown in FIG. 3. Thisdisplay 110, 304 may allow a user to ensure that end-effector 602 is ina desirable position in relation to robot arm 604, robot base 610, thepatient 210, and/or the user.

For example, as shown in FIG. 7A, markers 702 may be placed around thesurface of end-effector 602 so that a tracking device placed away fromthe surgical field 208 and facing toward the robot 102, 301 and thecamera 200, 326 is able to view at least 3 of the markers 702 through arange of common orientations of the end effector 602 relative to thetracking device 100, 300, 600. For example, distribution of markers 702in this way allows end-effector 602 to be monitored by the trackingdevices when end-effector 602 is translated and rotated in the surgicalfield 208.

In addition, in exemplary embodiments, end-effector 602 may be equippedwith infrared (IR) receivers that can detect when an external camera200, 326 is getting ready to read markers 702. Upon this detection,end-effector 602 may then illuminate markers 702. The detection by theIR receivers that the external camera 200, 326 is ready to read markers702 may signal the need to synchronize a duty cycle of markers 702,which may be light emitting diodes, to an external camera 200, 326. Thismay also allow for lower power consumption by the robotic system as awhole, whereby markers 702 would only be illuminated at the appropriatetime instead of being illuminated continuously. Further, in exemplaryembodiments, markers 702 may be powered off to prevent interference withother navigation tools, such as different types of surgical instruments608.

FIG. 8 depicts one type of surgical instrument 608 including a trackingarray 612 and tracking markers 804. Tracking markers 804 may be of anytype described herein including but not limited to light emitting diodesor reflective spheres. Markers 804 are monitored by tracking devicesassociated with the surgical robot system 100, 300, 600 and may be oneor more of the line of sight cameras 200, 326. The cameras 200, 326 maytrack the location of instrument 608 based on the position andorientation of tracking array 612 and markers 804. A user, such as asurgeon 120, may orient instrument 608 in a manner so that trackingarray 612 and markers 804 are sufficiently recognized by the trackingdevice or camera 200, 326 to display instrument 608 and markers 804 on,for example, display 110 of the exemplary surgical robot system.

The manner in which a surgeon 120 may place instrument 608 into guidetube 606 of the end effector 602 and adjust the instrument 608 isevident in FIG. 8. The hollow tube or guide tube 114, 606 of theend-effector 112, 310, 602 is sized and configured to receive at least aportion of the surgical instrument 608. The guide tube 114, 606 isconfigured to be oriented by the robot arm 104 such that insertion andtrajectory for the surgical instrument 608 is able to reach a desiredanatomical target within or upon the body of the patient 210. Thesurgical instrument 608 may include at least a portion of a generallycylindrical instrument. Although a screw driver is exemplified as thesurgical tool 608, it will be appreciated that any suitable surgicaltool 608 may be positioned by the end-effector 602. By way of example,the surgical instrument 608 may include one or more of a guide wire,cannula, a retractor, a drill, a reamer, a screw driver, an insertiontool, a removal tool, or the like. Although the hollow tube 114, 606 isgenerally shown as having a cylindrical configuration, it will beappreciated by those of skill in the art that the guide tube 114, 606may have any suitable shape, size and configuration desired toaccommodate the surgical instrument 608 and access the surgical site.

FIGS. 9A-9C illustrate end-effector 602 and a portion of robot arm 604consistent with an exemplary embodiment. End-effector 602 may furthercomprise body 1202 and clamp 1204. Clamp 1204 may comprise handle 1206,balls 1208, spring 1210, and lip 1212. Robot arm 604 may furthercomprise depressions 1214, mounting plate 1216, lip 1218, and magnets1220.

End-effector 602 may mechanically interface and/or engage with thesurgical robot system and robot arm 604 through one or more couplings.For example, end-effector 602 may engage with robot arm 604 through alocating coupling and/or a reinforcing coupling. Through thesecouplings, end-effector 602 may fasten with robot arm 604 outside aflexible and sterile barrier. In an exemplary embodiment, the locatingcoupling may be a magnetically kinematic mount and the reinforcingcoupling may be a five bar over center clamping linkage.

With respect to the locating coupling, robot arm 604 may comprisemounting plate 1216, which may be non-magnetic material, one or moredepressions 1214, lip 1218, and magnets 1220. Magnet 1220 is mountedbelow each of depressions 1214. Portions of clamp 1204 may comprisemagnetic material and be attracted by one or more magnets 1220. Throughthe magnetic attraction of clamp 1204 and robot arm 604, balls 1208become seated into respective depressions 1214. For example, balls 1208as shown in FIG. 9B would be seated in depressions 1214 as shown in FIG.9A. This seating may be considered a magnetically-assisted kinematiccoupling. Magnets 1220 may be configured to be strong enough to supportthe entire weight of end-effector 602 regardless of the orientation ofend-effector 602. The locating coupling may be any style of kinematicmount that uniquely restrains six degrees of freedom.

With respect to the reinforcing coupling, portions of clamp 1204 may beconfigured to be a fixed ground link and as such clamp 1204 may serve asa five bar linkage. Closing clamp handle 1206 may fasten end-effector602 to robot arm 604 as lip 1212 and lip 1218 engage clamp 1204 in amanner to secure end-effector 602 and robot arm 604. When clamp handle1206 is closed, spring 1210 may be stretched or stressed while clamp1204 is in a locked position. The locked position may be a position thatprovides for linkage past center. Because of a closed position that ispast center, the linkage will not open absent a force applied to clamphandle 1206 to release clamp 1204. Thus, in a locked positionend-effector 602 may be robustly secured to robot arm 604.

Spring 1210 may be a curved beam in tension. Spring 1210 may becomprised of a material that exhibits high stiffness and high yieldstrain such as virgin PEEK (poly-ether-ether-ketone). The linkagebetween end-effector 602 and robot arm 604 may provide for a sterilebarrier between end-effector 602 and robot arm 604 without impedingfastening of the two couplings.

The reinforcing coupling may be a linkage with multiple spring members.The reinforcing coupling may latch with a cam or friction basedmechanism. The reinforcing coupling may also be a sufficiently powerfulelectromagnet that will support fastening end-effector 102 to robot arm604. The reinforcing coupling may be a multi-piece collar completelyseparate from either end-effector 602 and/or robot arm 604 that slipsover an interface between end-effector 602 and robot arm 604 andtightens with a screw mechanism, an over center linkage, or a cammechanism.

Referring to FIGS. 10 and 11, prior to or during a surgical procedure,certain registration procedures may be conducted in order to trackobjects and a target anatomical structure of the patient 210 both in anavigation space and an image space. In order to conduct suchregistration, a registration system 1400 may be used as illustrated inFIG. 10.

In order to track the position of the patient 210, a patient trackingdevice 116 may include a patient fixation instrument 1402 to be securedto a rigid anatomical structure of the patient 210 and a dynamicreference base (DRB) 1404 may be securely attached to the patientfixation instrument 1402. For example, patient fixation instrument 1402may be inserted into opening 1406 of dynamic reference base 1404.Dynamic reference base 1404 may contain markers 1408 that are visible totracking devices, such as tracking subsystem 532. These markers 1408 maybe optical markers or reflective spheres, such as tracking markers 118,as previously discussed herein.

Patient fixation instrument 1402 is attached to a rigid anatomy of thepatient 210 and may remain attached throughout the surgical procedure.In an exemplary embodiment, patient fixation instrument 1402 is attachedto a rigid area of the patient 210, for example a bone that is locatedaway from the targeted anatomical structure subject to the surgicalprocedure. In order to track the targeted anatomical structure, dynamicreference base 1404 is associated with the targeted anatomical structurethrough the use of a registration fixture that is temporarily placed onor near the targeted anatomical structure in order to register thedynamic reference base 1404 with the location of the targeted anatomicalstructure.

A registration fixture 1410 is attached to patient fixation instrument1402 through the use of a pivot arm 1412. Pivot arm 1412 is attached topatient fixation instrument 1402 by inserting patient fixationinstrument 1402 through an opening 1414 of registration fixture 1410.Pivot arm 1412 is attached to registration fixture 1410 by, for example,inserting a knob 1416 through an opening 1418 of pivot arm 1412.

Using pivot arm 1412, registration fixture 1410 may be placed over thetargeted anatomical structure and its location may be determined in animage space and navigation space using tracking markers 1420 and/orfiducials 1422 on registration fixture 1410. Registration fixture 1410may contain a collection of markers 1420 that are visible in anavigational space (for example, markers 1420 may be detectable bytracking subsystem 532). Tracking markers 1420 may be optical markersvisible in infrared light as previously described herein. Registrationfixture 1410 may also contain a collection of fiducials 1422, forexample, such as bearing balls, that are visible in an imaging space(for example, a three dimension CT image). As described in greaterdetail with respect to FIG. 11, using registration fixture 1410, thetargeted anatomical structure may be associated with dynamic referencebase 1404 thereby allowing depictions of objects in the navigationalspace to be overlaid on images of the anatomical structure. Dynamicreference base 1404, located at a position away from the targetedanatomical structure, may become a reference point thereby allowingremoval of registration fixture 1410 and/or pivot arm 1412 from thesurgical area.

FIG. 11 provides an exemplary method 1500 for registration consistentwith the present disclosure. Method 1500 begins at step 1502 wherein agraphical representation (or image(s)) of the targeted anatomicalstructure may be imported into system 100, 300 600, for example computer408. The graphical representation may be three dimensional CT or afluoroscope scan of the targeted anatomical structure of the patient 210which includes registration fixture 1410 and a detectable imagingpattern of fiducials 1420.

At step 1504, an imaging pattern of fiducials 1420 is detected andregistered in the imaging space and stored in computer 408. Optionally,at this time at step 1506, a graphical representation of theregistration fixture 1410 may be overlaid on the images of the targetedanatomical structure.

At step 1508, a navigational pattern of registration fixture 1410 isdetected and registered by recognizing markers 1420. Markers 1420 may beoptical markers that are recognized in the navigation space throughinfrared light by tracking subsystem 532 via position sensor 540. Thus,the location, orientation, and other information of the targetedanatomical structure is registered in the navigation space. Therefore,registration fixture 1410 may be recognized in both the image spacethrough the use of fiducials 1422 and the navigation space through theuse of markers 1420. At step 1510, the registration of registrationfixture 1410 in the image space is transferred to the navigation space.This transferal is done, for example, by using the relative position ofthe imaging pattern of fiducials 1422 compared to the position of thenavigation pattern of markers 1420.

At step 1512, registration of the navigation space of registrationfixture 1410 (having been registered with the image space) is furthertransferred to the navigation space of dynamic registration array 1404attached to patient fixture instrument 1402. Thus, registration fixture1410 may be removed and dynamic reference base 1404 may be used to trackthe targeted anatomical structure in both the navigation and image spacebecause the navigation space is associated with the image space.

At steps 1514 and 1516, the navigation space may be overlaid on theimage space and objects with markers visible in the navigation space(for example, surgical instruments 608 with optical markers 804). Theobjects may be tracked through graphical representations of the surgicalinstrument 608 on the images of the targeted anatomical structure.

FIGS. 12A-12B illustrate imaging devices 1304 that may be used inconjunction with robot systems 100, 300, 600 to acquire pre-operative,intra-operative, post-operative, and/or real-time image data of patient210. Any appropriate subject matter may be imaged for any appropriateprocedure using the imaging system 1304. The imaging system 1304 may beany imaging device such as imaging device 1306 and/or a C-arm 1308device. It may be desirable to take x-rays of patient 210 from a numberof different positions, without the need for frequent manualrepositioning of patient 210 which may be required in an x-ray system.As illustrated in FIG. 12A, the imaging system 1304 may be in the formof a C-arm 1308 that includes an elongated C-shaped member terminatingin opposing distal ends 1312 of the “C” shape. C-shaped member 1130 mayfurther comprise an x-ray source 1314 and an image receptor 1316. Thespace within C-arm 1308 of the arm may provide room for the physician toattend to the patient substantially free of interference from x-raysupport structure 1318. As illustrated in FIG. 12B, the imaging systemmay include imaging device 1306 having a gantry housing 1324 attached toa support structure imaging device support structure 1328, such as awheeled mobile cart 1330 with wheels 1332, which may enclose an imagecapturing portion, not illustrated. The image capturing portion mayinclude an x-ray source and/or emission portion and an x-ray receivingand/or image receiving portion, which may be disposed about one hundredand eighty degrees from each other and mounted on a rotor (notillustrated) relative to a track of the image capturing portion. Theimage capturing portion may be operable to rotate three hundred andsixty degrees during image acquisition. The image capturing portion mayrotate around a central point and/or axis, allowing image data ofpatient 210 to be acquired from multiple directions or in multipleplanes. Although certain imaging systems 1304 are exemplified herein, itwill be appreciated that any suitable imaging system may be selected byone of ordinary skill in the art.

Turning now to FIGS. 13-16, the surgical robot system 100, 300, 600relies on accurate positioning of the end-effector 112, 602, surgicalinstruments 608, and the patient 210 (e.g., patient tracking device 116)relative to the desired surgical area. As best seen in FIG. 14, aninfrared signal based method may be used to determine the 3-dimensionalposition of the tracking markers described herein, such as markers 118,702 and the like. In an exemplary embodiment, the infrared signal methoddescribed herein may be especially suitable with active markers 702 onthe end-effector 112, 602 and/or passive markers 118 on the surgicalinstrument 608 or the patient tracking device 116.

As shown in FIGS. 13 and 14, an infrared signal transmitter (e.g.,infrared LED) 1602 is capable of transmitting an infrared signal 1600which can be comprised of a burst signal 1604, non-burst signal 1606, ora combination of both as shown. The infrared signal 1600 may be in theform of a burst pattern. For example, the burst pattern may include theburst signal 1604 for a fixed amount of time and a non-burst signal 1606for a fixed amount of time. This burst pattern may repeat for a givenamount of time. The burst pattern may include any suitable combinationof the burst signal 1604 and the non-burst signal 1606 for any suitableduration. For example, the frequency of the burst signal 1604 can beabout 110 KHz with a burst duration of about 340 μsec. The duration ofthe non-burst signal 1606 can be about 730 μsec. Infrared signaltransmitters 1602 and infrared signal detectors D1 can be incorporatedwith the camera or cameras 200, 326. Alternatively, the infrared signaltransmitters 1602 and infrared signal detectors D1 can be attached to aportion of the camera stand 202, for example, near or proximate to thecamera or cameras 200, 326.

The robot-assisted surgery system 100, 300, 600 uses an improvedcircuit/device 1672 for regenerating an infrared signal transmitted overthe air for use in determining a 3-dimensional position of an object,such as the surgical tool 608. The infrared signal regeneration device1672 of FIG. 14 amplifies the received infrared signal as Vsig andcreates a reference signal Vref which is slightly below Vsig. Theregeneration device 1672 then peak detects the amplitude of Vsig bycomparing its level to Vref, thus creating a toggling voltage for theburst signal 1604, and a single edge for the non-burst signal 1606.

As previously described, tracking markers 118, 702, such as sphericalballs (objects to be tracked) 208 can be positioned on the surgical tool608, the end-effector 112, 602, the patient 210, or other suitablelocations. As identified in FIG. 14 as spherical ball 1608, thetransmitted signal 1600 may be reflected from the one or more sphericalballs 1608 and the reflected signal in the form of a responsive signal1664 is received by infrared detectors D1. Alternatively, in a systemwith active sensors, for example, tracking markers 702 on end-effector601 in FIGS. 7A-7C, the objects 1608 include their own infraredtransmitters 1662 which transmit an infrared signal with a known pattern(e.g., the same waveform pattern as received) in response to theinfrared signal transmitted by the transmitters 1602.

A responsive infrared signal 1664 (transmitted by infrared transmittersin the objects 1608 in response to the signal from the infraredtransmitter 1602 in the case of an active sensor or reflected by theobjects from the signal from the infrared transmitter 1602 in the caseof a passive sensor) is received by the infrared detectors D1 in analogform. While only one is shown in FIG. 14 for illustrative purpose, thereare typically multiple infrared detectors that are strategicallypositioned in the robotic system 100, 300, 600.

The analog signal 1664 received by the infrared detectors D1 is then fedinto an amplifier 1666. The amplifier can be, for example, a relativelyinexpensive operational amplifier, such as part no. OPA2381 from TexasInstruments of Dallas, Tex. Although only one amplifier 1666 is shown,amplification of the analog signal 1664 may involve multiple amplifiersthat are coupled in parallel or in series or both.

The output of the amplifier 1666 is fed into a diode D2 which isconnected to a low pass filter 1668. The diode provides a small voltagedrop to prepare the signal for comparison against the original outputVsig of the amplifier 1666. The diode D2 can be, for example, a Schottkydiode having a forward bias voltage of about 400 mV. A Schottky diodemay be preferable to a normal p-n junction type diode due to its fastresponse time.

The low pass filter 1668 includes an RC circuit (resistor R1, capacitorC1) and resistor R2 connected in parallel to the capacitor C1. Theresistors R1 and R2 act as a voltage divider to divide the output of thediode D2. The values of the resistors R1, R2 can be, for example, 300Ohms and 5 KOhms, respectively. Accordingly, most of the voltage dropoccurs over the resistor R2.

As can be seen in FIG. 14, the output Vref of the low pass filter 1668is the same as the voltage divider output. The output Vref is fed intoone input (− input) of a comparator 1670 while the output of theamplifier 16266 is fed into the other input (+ input) of the comparator.The comparator 1670 can be, for example, a CMOS comparator, such as partno. TLV7211 from Texas Instruments of Dallas, Tex.

Referring to FIGS. 14 and 16, the operation of the signal regenerationcircuit 1672 will now be described. At the output of the amplifier 1666,the amplified signal may not be a perfectly scaled replica of the inputdue to bandwidth and output slew limitations of the amplifier. Accordingto one aspect of the present invention, however, this is acceptable forreasons now described.

D2, R1, C1 and R2 form a passive peak detector, and a voltage level V_(ref) is generated. Its average value is:

$\begin{matrix}{{\overset{¯}{V}}_{ref} = {{V_{sigpk} \cdot \frac{R2}{{R2} + {R1}}} - V_{D\; 2f}}} & (1)\end{matrix}$

Where:

-   -   V_(sigpk)=peak voltage of the amplified infrared signal Vsig;    -   V_(D2f)=forward voltage of D2.

The voltage signal Vref is fed to the comparator 1670 and is comparedagainst Vsig. Based on the comparison, the comparator 1670 generates avoltage Vout representing the low and high logic states which can beused by a digital signal processor for determining the 3-dimensionalpositions of the various objects being tracked. In other words, thecomparator 1670 converts an analog signal into a digital signal, whichcan be easily processed by a processor 1646 such as a microcontroller orsimilar devices.

FIG. 16 shows the waveforms Vsig, Vref and Vout when the infrareddetector D1 receives the responsive infrared signal 1664 which may be areflection of the infrared signal 1600 transmitted by the infraredtransmitter 1602. Due to limitations of the bandwidth and output slew ofthe amplifier, the signal Vsig appears as a sinusoidal wave, rather thanthe original signal 1600 with sharply defined leading and falling edges.

The signal Vref is lower in voltage than the signal Vsig. The amount ofthe voltage drop is predetermined based on the forward bias voltage dropof the diode D2 and the voltage drop across the resistor R1. The signalVref has a relatively flat waveform due to the low pass filter 268.

The comparator 1670 generates a logic high signal (e.g., 5 Volt signal)when Vsig is greater than Vsig and a logic low signal (e.g., 0 Voltsignal) when Vsig falls below Vref. As can be seen, the voltage at Vrefis proportional to Vsig. At lower voltages (i.e., when the distancebetween the object 1608 and the infrared detector D1 is relatively long,the difference between Vsig and Vref may not be sufficient to toggle thecomparator 1670 without the presence of the diode D2. The diode D2ensures that there is at least a preset voltage difference between Vsigand Vref (i.e., forward bias voltage of diode D2). Thus, the presence ofa diode D2 between the operational amplifier 1666 and the low passfilter 1668 may be important.

As can be seen by the waveform Vout in FIG. 16, it generates a fairlyaccurate regeneration of the original signal 1600 over longer distancebetween the infrared transmitter 1602 and the objects 1608 even thoughthe responsive signal 1664 has been substantially degraded.

Advantageously, this configuration relaxes the requirement of a highbandwidth, high slew output amplification. It is also not as sensitiveto amplitude variations as simple amplification would be. This isbecause as Vsig decreases when the distance between the objects 1608 andinfrared transmitter 1602 becomes longer, Vref also decreases. Thatallows the comparator 1670 to continue to toggle correctly when needed.This results in the effective working distance between the objects 1608and infrared transmitter 1602 to increase by 75%-200% (7-10 meters).

FIG. 15 is a functional diagram of an infrared signal based positionrecognition system 1640 for use with a robot-assisted surgery accordingto an aspect of the present invention.

The system 1640 is connected to the output of the comparator 1670through a communication link 1652 which is connected to an I/O interface1642, which receives information from and sends information over thecommunication link 1652. The system 1640 includes memory storage 1644such as RAM (random access memory), processor (CPU) 1646, programstorage 1648 such as FPGA, ROM or EEPROM, and data storage 1650 such asa hard disk, all commonly connected to each other through a bus 1653.The program storage 1648 stores, among others, a position recognitionmodule 1654 containing software to be executed by the processor 1646.The position recognition module 1654 receives the digital waveform Voutthrough the communication link 1652 and determines the 3-dimensionalposition of the object 1608 based on the digital waveform, shape of theamplified signals, known locations of the objects and infrared detectorsD1, and possibly the time it took to receive the responsive signals1664. The position recognition module 1654 may also determine the3-dimensional position of the objects 1608 with the help of the cameras200, 326 (e.g. stereo cameras) and the tracking system 100, 300, 600.The camera or cameras 200, 326 can record regular optical images orinfrared images or both.

The position recognition module 1654 also determines whether the objectsbeing tracked are passive or active objects by analyzing the time ittakes for the responsive signals to be received from the time theinitial signal 1606 is transmitted. Since active objects will have alonger known delay amount between the transmission of signal 1606 andthe receipt of the responsive signal, the module 1654 can distinguishthe type of objects (e.g., passive or active) being tracked.

The position recognition module 1654 includes a user interface modulethat interacts with the user through the display device 1611 and inputdevices such as keyboard 1612 and pointing device 1614 such as arrowkeys, mouse or track ball. The user interface module assists the user inprogramming the module 1654 to perform 3-dimensional positionrecognition of the objects 1608. Any of the software program modules inthe program storage 1648 and data from the data storage 1650 can betransferred to the memory 1644 as needed and is executed by the CPU1646.

One exemplary system 1640 may be 8051 microcontroller from IntelCorporation of Santa Clara, Calif. However, any digital signalprocessor, processor or microcontroller can be used.

In one embodiment, parts of or the entire system 1640 including theinput devices 1612, 1614 and display device 1611 can be incorporatedinto the robot system 100, 300, 600 or any suitable robotic surgicalsystem. For example, the display 1611 can be the same as display 110,304.

While the position recognition system 1640 has been described withreference to an infrared signal, the principles disclosed herein couldbe used with any optical signal as well as other signals such asultrasound signal. Also, while only a single infrared signal has beendescribed, the present system can transmit a set of infrared signalshaving either different wavelengths or waveform shapes each forreflection or transmission by a respective spherical ball to be tracked.

Although several embodiments of the invention have been disclosed in theforegoing specification, it is understood that many modifications andother embodiments of the invention will come to mind to which theinvention pertains, having the benefit of the teaching presented in theforegoing description and associated drawings. It is thus understoodthat the invention is not limited to the specific embodiments disclosedhereinabove, and that many modifications and other embodiments areintended to be included within the scope of the appended claims.Moreover, although specific terms are employed herein, as well as in theclaims which follow, they are used only in a generic and descriptivesense, and not for the purposes of limiting the described invention, northe claims which follow.

It will be appreciated by those skilled in the art that while theinvention has been described above in connection with particularembodiments and examples, the invention is not necessarily so limited,and that numerous other embodiments, examples, uses, modifications anddepartures from the embodiments, examples and uses are intended to beencompassed by the claims attached hereto. The entire disclosure of eachpatent and publication cited herein is incorporated by reference, as ifeach such patent or publication were individually incorporated byreference herein. Various features and advantages of the invention areset forth in the following claims.

What is claimed is:
 1. A method for regenerating an infrared signaltransmitted over the air for use in detecting a 3-dimensional positionof an object, comprising: transmitting an infrared signal, via atransmitter, over the air towards an object whose position is to bedetermined; receiving, via an infrared signal detector, from the objecta responsive infrared signal in response to the transmitted infraredsignal; receiving the responsive infrared signal at a low pass filterand outputting a filtered signal; and generating, at a comparator, acomparator output representing a logic state based on a first inputreceiving the responsive infrared signal from the infrared signaldetector and a second input receiving the filtered signal from the lowpass filter.
 2. The method of claim 1, further comprising: receiving, atthe infrared signal detector, a reflection of the infrared signaltransmitted by the infrared signal transmitter as the responsiveinfrared signal.
 3. The method of claim 1, further comprising:generating an amplified responsive infrared signal via an amplifiercoupled between the infrared signal detector and the low pass filter. 4.The method of claim 3, further comprising: reducing the voltage of theamplified responsive infrared signal by a predetermined amount via adiode connected between the amplifier and the low pass filter.
 5. Themethod of claim 4, wherein the diode has a forward bias voltage of 0.4Volt or less.
 6. The method of claim 4, wherein the diode includes aSchottky diode.
 7. The method of claim 1, further comprising: reducingthe voltage of the amplified responsive infrared signal by apredetermined amount via a diode connected between the amplifier and thelow pass filter, wherein the low pass filter includes a capacitorcoupled between the diode and ground.
 8. The method of claim 1, whereinthe low pass filter includes: a voltage divider having first and secondresistors connected in series between the output of the infrared signaldetector and ground, a node between the first and second resistorsdefining an output of the voltage divider; a capacitor coupled betweenthe voltage divider output and ground.
 9. The method of claim 1, furthercomprising: receiving the comparator output at a signal processor anddetermining a 3-dimensional position of the object.
 10. A method forrecognizing a position of an object via an infrared signal for use witha robot-assisted surgery comprising: transmitting an infrared signal,via an infrared signal transmitter, over the air towards an object whoseposition is to be determined; receiving, via an infrared signalreceiver, from the object a responsive infrared signal in response tothe transmitted infrared signal; receiving the responsive infraredsignal at a low pass filter and outputting a filtered signal;generating, at a comparator, a comparator output representing a logicstate based on a first input receiving the responsive infrared signalfrom the infrared signal detector and a second input receiving thefiltered signal from the low pass filter; receiving the comparatoroutput at a signal processor and determining a 3-dimensional position ofthe object.
 11. The position recognition system of claim 10, generatingan amplified responsive infrared signal via an amplifier coupled betweenthe infrared signal detector and the low pass filter.
 12. The method ofclaim 11, further comprising: reducing the voltage of the amplifiedresponsive infrared signal by a predetermined amount via a diodeconnected between the amplifier and the low pass filter.
 13. The methodof claim 10, further comprising: reducing the voltage of the amplifiedresponsive infrared signal by a predetermined amount via a diodeconnected between the amplifier and the low pass filter, wherein the lowpass filter includes a capacitor coupled between the diode and ground.14. The method of claim 10, wherein the low pass filter includes: avoltage divider having first and second resistors connected in seriesbetween the output of the infrared signal receiver and ground, a nodebetween the first and second resistors defining an output of the voltagedivider; a capacitor coupled between the voltage divider output andground.
 15. A method for recognizing a position of an object via aninfrared signal for use with a surgical robot system, said methodcomprising: transmitting an infrared signal, via a transmitter, over theair towards an object whose position is to be determined; receiving, viaan infrared signal detector, from the object a responsive infraredsignal in response to the transmitted infrared signal; receiving theresponsive infrared signal at a low pass filter and outputting afiltered signal; and generating, at a comparator, a comparator outputrepresenting a logic state based on a first input receiving theresponsive infrared signal from the infrared signal detector and asecond input receiving the filtered signal from the low pass filter,wherein the surgical robot system includes: a robot having a robot baseand a display, a robot arm coupled to the robot base, and anend-effector coupled to the robot arm, the end-effector having one ormore tracking markers, wherein movement of the end-effector iselectronically controlled by the robot; and a camera stand including atleast one camera able to detect the one or more tracking markers, thecamera including at least one infrared signal detector that receivesfrom the one or more tracking markers an infrared signal, wherein therobot determines a 3-dimensional position of the one or more trackingmarkers based on the infrared signal, and wherein the infrared signalincludes a burst signal.
 16. The system of claim 15, wherein theinfrared signal includes a burst pattern including the burst signal fora fixed amount of time and a non-burst signal for a fixed amount oftime.
 17. The method of claim 15 wherein the surgical robot systemincludes at least one infrared signal transmitter attached to a portionof the camera stand that transmits an infrared signal towards the one ormore tracking markers whose position is to be determined.
 18. The methodof claim 17, wherein the at least one infrared signal transmittertransmits an infrared signal comprised of a burst signal, a non-burstsignal, or a combination of both.
 19. The method of claim 15, whereinthe one or more tracking markers in the end-effector are active markershaving an active state and an inactive state, the active state emittingthe infrared signal.
 20. The method of claim 15 wherein the surgicalrobot system further includes a surgical instrument having one or moretracking markers to be tracked by the robot system, the surgicalinstrument configured to be positioned in the end-effector in order toalign the surgical instrument along a given trajectory for a surgicalprocedure.